The following charts compare various type of coaxial cable used in VHF and UHF data radio systems. All coax cable has a certain amount of signal loss. When an antenna is connected to a radio modem using any type of coax cable, the transmit signal is attenuated as it passes through the cable, so the actual transmit radio power into the air is less than the amount of power the radio puts out.

Also, when a data radio modem is receiving a signal, the receive signal that reaches the radio’s receiver will be weaker than the signal that reached the antenna. The received signal will be attenuated as it travels down the coax cable to the radio’s receiver. If you want your data radio system to have the widest possible coverage, you should minimize your coax cable losses.

The amount of coax cable attenuation primarily depends upon the diameter of the cable and the dielectric material used to insulate the center conductor. Small diameter cables are easier to install and use, but small diameter cables loose a lot more signal than the larger-diameter versions. For cable runs less than a few feet, any cable type will do. For coax cable runs 10-20 feet, you may consider using lower-cost middle-sized cable such as RG-58. For cable runs of over 20 feet, consider using the best quality cable you can afford (if you are trying to build a system with wide coverage and high reliability).

Coax Cable Comparison (English)

Cable Group

Attenuation in dB per 100 feet

Outer Diameter (inches)

30

50

100

150

450

1000

2400

LMR-100A®

3.9

5.1

7.2

8.9

15.8

24.1

38.0

LMR-200®

1.8

2.3

3.2

4.0

7.0

10.4

16.5

0.195

LMR-240 Ultra®

1.3

1.7

2.9

3.6

5.3

9.5

12.7

0.240

LMR-240®

1.3

1.7

2.4

3.0

5.2

7.9

12.7

0.240

LMR-400 Ultra®

0.8

1.1

1.5

1.5

3.2

5.0

7.9

0.405

LMR-400®

0.7

0.9

1.3

1.5

2.7

4.1

6.6

0.405

RG-174

5.5

6.6

8.8

10.3

18.1

27.4

43.0

0.100

RG-213

1.0

1.5

2.1

2.8

4.4

7.1

12.0

0.405

RG-214

1.2

1.6

1.9

2.4

5.1

8.0

13.7

0.405

RG-316

4.3

5.6

7.9

4.4

17.2

26.1

45.0

0.110

RG-58A/U

2.5

4.1

5.3

6.1

10.6

24.0

38.9

0.195

RG-8/U FOAM

1.0

1.2

1.8

2.4

4.4

7.1

12.0

0.400

RG-8X

2.0

2.1

3.0

4.7

8.6

12.9

21.6

0.242

RG218/U

0.4

0.6

0.8

1.0

2.0

3.8

6.4

0.870

The chart above is in English units. Below is the same data, in metric: